1. Field of the Invention
This invention relates in general to certain new and useful improvements in an apparatus and method for controlling the opening and closing movement of gates, and more particularly, to an apparatus and method for automatically controlling the movement of gates on a highly efficient basis and which enables a gate to remain unlocked at the closed position until an opening movement force is applied to the gate.
2. Brief Description of the Prior Art
Over the years, a variety of types and styles of gates have been developed to provide security for such areas as parking structures and entrances and exits to residential and industrial properties. These gates may take the form of sliding gates which move in or on a track, or swinging gates which are rotatably hinged to a fixed structure. Where large passageways are involved, gates may be provided in pairs which operate from opposite sides of the openings.
Many control systems have been developed to provide automatic control for the opening and closing of gates. These control systems include an electric motor operatively connected to the gate to control its movement. Typically, the motor is controlled by a switch in the vicinity of the gate which can only be operated by authorized personnel. For example, the switch may be in the form of a key switch which can only be operated by use of a conventional key or by a card key.
Various prior art control systems also employ means for mechanically sensing when the gate is in its fully opened or fully closed position. These sensing means are typically in the form of limit switches which are used to deenergize the motor when the gate has reached its end position of travel. The limit switches must be individually adjusted for each gate installation to ensure proper alignment with the opened and closed positions of the gate. In addition, because of the mechanical nature of the limit switches, they tend to wear and change in their adjustment, resulting in improper gate operation.
In addition to detecting the opened and closed positions of the gate, safety considerations require means for detecting if the gate has encountered an obstruction in its travel. For example, such obstructions might be caused by a vehicle or pedestrian in the path of the gate while it is being operated. When an obstruction is detected, gate motion must be stopped to avoid damage to either the gate or the obstruction or injury to people.
In most of the prior art gate opening and closing mechanisms, a positive locking mechanism was provided to physically and automatically lock the gate when it reached the closed position. In this way, only authorized access to a controlled area was achieved. Many of these prior art positive locking mechanisms relied upon the use of a solenoid operated lock which included a locking pin on the gate capable of being inserted into an opening on a fixed structure at the gate closed position. However, in each case, the gate was automatically and positively locked when it reached the closed position.
The locking of the gate at the closed position, while effective to provide a measure of security, poses many problems to the occupants of the controlled area as well as to public officials. If for some reason, there is a malfunction of the gate operating mechanism, it automatically locks at the closed position and the occupants on the inside of the controlled area would not have egress through the access opening covered by the gate. Thus, some means to physically unlock the gate has to be provided. In addition, in the event of a power failure which could arise, as a result of disruption from an electrical utility supplier or as a result of a fire, it is necessary for public officials to have access to the controlled or secured area. Thus, some fire departments and other health control officials require a special unlocking mechanism located at the exterior of the gate and which is confined in a locked box or similar secured area to which they have special access. Many fire department or other health or other public officials require a special key for access to these locked boxes or secured containers.
In addition to the above, each of the prior art locking mechanisms also uses a complex gear structure for purposes of driving the gate between the opened and closed positions. While these gear boxes are effective, they are noisy and consume a substantial amount of the power generated by the electric motor. Moreover, it is virtually impossible to push a gate against the action of the gear box in the event of a power failure.
There have also been gate opening and closing apparatus which utilize sensors, such as optical sensors, for measuring the extent of movement of the gate between the opened and closed positions and thereafter controlling the gate during movements for the measured distance. In this way, the gate opening and closing apparatus will effectively measure the distance of the first movement of the gate and thereafter move the gate for that same distance during each subsequent opening and closing movement. One such opening and closing apparatus is more fully illustrated and described in U.S. Pat. No. 4,429,264, dated Jan. 31, 1984 by Moscow K. Richmond, for "System and Method For The Automatic Control Of Electrically Operated Gates".
There are many substantial drawbacks to the use of optical sensors for purposes of distance measuring. There is usually a substantial problem of dirt collection on the optical sensor which impairs the optical measuring system and which also requires frequent maintenance. More commonly, as a result of the operating equipment, grease and oil, which are regularly applied to the equipment for maintenance purposes, also tend to collect on the optical sensor thereby impairing the operation of the optical sensor.
U.S. Pat. No. 4,159,599, dated July 3, 1979 by Moscow K. Richmond for "Gate Opening and Closing Assembly" discloses a gate which is slidable between opened and closed positions and which uses a solenoid operated locking mechanism. U.S. Pat. No. 4,313,281, dated Feb. 2, 1982 by Moscow K. Richmond for "Gate Opening and Closing Apparatus and Method" also discloses a positive locking mechanism for use in locking a gate when it reaches a gate closed position. U.S. Pat. No. 4,330,958 by Moscow K. Richmond, dated May 25, 1982 for "Gate Opening and Closing Assembly With Automatic Locking Means" also discloses a gate opening and closing assembly with an automatic locking mean for locking the gate when it reaches a closed position.